The present invention relates to an automatic valve for reducing compression during start of a two-stroke internal combustion engine, comprising a movable valve adapted to control a gas flow through an opening in a wall of the combustion chamber of the engine, a resilient means for moving the movable valve to an open position, and a driver actuated by an underpressure and adapted to move the movable valve to a closed position against the action of the resilient means.
The decompression valve according to the invention has the purpose of facilitating the starting of internal combustion engines of the type started either manually by means of a rope starter or the like, or by an electric starter motor. For the intended purpose, a plurality of valve designs adapted to automatic operation have been previously proposed. Such prior art valves are disclosed in, for example, DE 1949541, U.S. Pat. No. 5,050,546 and DE 4403609. It has appeared, however, that the prior art valves known from these publications do not operate satisfactorily and, as far as is known, have therefore not been used in practice.